This invention relates generally to sampling means and methods and relates, more particularly, to the means and methods for sampling surface array spots having analytes.
In earlier U.S. Pat. No. 6,803,566, having the same assignee as the instant application, a sampling technique is disclosed which involves the sampling of surface array spots having analytes. More specifically, the described sampling technique utilizes a tipped probe and an associated self-aspirating emitter through which a liquid agent, such as a eluting solvent, is delivered to the surface array and through which samples are conducted from the surface array for purposes of analysis. In addition, a positioning system is provided for automatically translating the surface array along X and Y-coordinate axes (i.e. within the plane of the surface array) to alter the position of the surface array relative to the probe. In other words, by shifting the surface array relative to the probe along X and Y coordinate directions, the tip of the probe can be positioned in registry with any spot (i.e. any X-Y coordinate location) along the surface array. Thereafter, the surface array and tip of the probe can be manually moved toward one another (i.e. along the Z-coordinate axis) until a liquid microjunction is presented between the tip of the probe and the surface array, and it is in this probe-to-surface array condition that the corresponding spot on the array is sampled with the probe. The sample is thereafter conducted to appropriate test equipment where the desired analysis of the sample is carried out. The probe used in such a sampling technique is particularly well-suited as an interface for coupling thin-layer chromatography and mass spectrometry. The referenced patent describes the sampling technique as being useful in the field of proteomics in which protein microarrays are analyzed, but other uses can be had.
Heretofore and as suggested above, the spaced relationship between the tip of the probe and surface array (i.e. along the Z-coordinate axis) to effect the initial formation of the liquid microjunction and to thereafter maintain an optimum microjunction thickness during the course of an experiment has required the intervention of an operator. In other words, it is an operator who has been required to manually position the tip of the probe and the surface array adjacent one another for sampling purposes and to make manual adjustments, as necessary, of the probe-to-surface array distance throughout the course of the sampling procedure. Furthermore, the collection of a plurality of samples from different spots or alternative development lanes (e.g. along an X or Y-coordinate path) upon the surface array is likely to involve additional operator-controlled, i.e. manual, adjustment, of the distance between the tip of the probe and the surface array. Consequently and as a result of the necessary involvement of an operator during the control of the probe-to-surface array distance during a sampling technique of the prior art, the precision of this prior art sample-collection technique typically corresponds to the skill of the operator involved.
It would be desirable to provide the aforedescribed sampling technique with a means for automatically controlling the probe-to-surface array distance during the collection of samples from surface array spots or development lanes.
Accordingly, it is an object of the present invention to provide a new and improved system and method for automatically controlling the distance between the sampling probe and the surface of the array to be sampled with the probe which does not require operator intervention during a sample-collecting operation.
Another object of the present invention is to provide such a system and method wherein the probe and surface array are automatically positioned in a desirable spaced relationship for purposes of sampling the surface array with the probe.
Still another object of the present invention is to provide such a system and method wherein the probe-to-surface distance is continually monitored throughout the sampling procedure and adjusted, as necessary, so that the probe-to-surface distance is maintained at an optimal spacing.
Yet another object of the present invention is to provide such a system which is uncomplicated in structure, yet effective in operation.